Oxfam activists staging a protest Thursday at the Paris climate talks wear masks of from left, U.S. President Barack Obama, Chinese President Xi Jinping, French President Francois Hollande, Indian Prime Minister Narendra Modi, German Chancellor Angela Merkel and Australian Prime Minister Malcolm Turnbull. (Christophe Ena/AP)

The Paris talks had just reached the halfway point when a small band of climate skeptics made their stand at a hotel on the opposite side of town. With charts and slides, the group repeated a claim that is familiar to Washington but wildly out of sync with the discussions here: Man-made global warming is a fiction.

“To limit CO2 emissions is not only wasteful but also counterproductive,” Fred Singer, a Virginia physicist and longtime critic of the scientific consensus on climate change, told the gathering, billed as an exercise to “bring climate realism to Paris.”

But at the real climate talks north of the city, such views were nowhere to be found. As negotiations entered their 11th day on Thursday, diplomats representing nearly every nation on Earth gathered in noisy conference rooms to haggle over the scope and timing of a proposed international accord on fighting the causes of climate change. They argued, sometimes passionately, over the costs of the pact and over how to pay for it. But they did not debate whether the problem is real.

Indeed, doubts about the science of climate change — once a staple of international climate talks, used by nations as well as energy companies to argue against controls on fossil-fuel emissions — appears to have vanished from the public discourse here, relegated to side events organized by veteran climate skeptics, or by visitors from the one major legislative body that has actively sought to block a climate agreement in Paris: the U.S. Congress.

“They are the lone holdouts,” Alden Meyer, director of strategy and policy for the Union of Concerned Scientists, said of the denier caucus that dominates the Republican majority in both the House and Senate. “On this issue, the only dysfunction you see these days is in the United States — and, really, just in Washington.”

The Republicans appear to be one of the only political parties in control of a legislature in the industrialized world to espouse the contrarian view on climate change. This week, Republican leaders took advantage of the climate conference to reiterate their skepticism about man-made global warming and their opposition to any agreement in Paris that would commit the United States to doing something about it.

“The president plans to reach a climate change deal that ignores the American people and cuts them out of the process entirely,” Sen. John Barrasso (R-Wyo.), chairman of the Senate Republican Policy Committee, said Wednesday in a speech on the Senate floor. “The American public doesn’t want these policies.”

At the Paris skeptics’ summit, held in the downtown hotel a few miles from the climate talks, the chairman of the Senate Environment and Natural Resources Committee appeared via video to denounce the international negotiations as “full of hot air.”

“The commitments that the president made in Paris aren’t going to happen,” Sen. James M. Inhoffe (R-Okla.) said. “The American people have caught on to the president’s climate charade.”

But here, such opinions are seen as strikingly out of step, if not anachronistic.

Indeed, 18 years after the failure of the Kyoto climate treaty, a broad international consensus appears to have emerged on climate change: Despite lingering discord over the particulars, countries across the political and economic spectrum are lining up in support of an accord limiting emissions from the burning of fossil fuels.

In Paris, staunch foes of past climate agreements, including Saudi Arabia and other oil-rich states, expressed support Wednesday for international action to limit the rise in global temperatures to less than 2 degrees Celsius over pre-industrial levels.

“Saudi Arabia wants an agreement that will achieve climate goals hand in hand with sustainable development goals,” a Saudi spokesman said in a statement to The Washington Post.

The diplomatic support for a climate agreement comes as titans of the corporate world, from Google and Facebook to energy companies such as Royal Dutch Shell, also have renewed calls in recent days for aggressive measures to fight climate change. On Tuesday, American Electric Power, one of the largest U.S. electric utilities, became the latest to withdraw from the American Legislative Exchange Council, an organization that has opposed action on climate change.

Environment Protection Agency Administrator Gina McCarthy, in France to support the U.S. delegation to the talks, described a “new dynamic” in Paris, with corporate leaders often taking positions ahead of politicians.

“They see the seriousness of the problem,” McCarthy said. “There are no climate skeptics hanging around here . . . because the rest of the world has moved on.”

Apart from Congress, most Americans have moved on as well, said McCarthy, citing polls that show large majorities of Americans favoring action to address climate change.

“There are some members of Congress who clearly want to send other signals,” she said, “but I don’t think those signals have reached this body.”